Fabrication of NiO and TiO2 supported nano calcium carbonate and its effect on the flame retardancy and thermal stability of epoxy resin composites

Nano calcium carbonate (CaCO3) was successfully treated by tetrabutyl titanate sol together with nickel hydroxide, followed by calcination to form a new kind of flame retardant (Ni-TiO2@CaCO3). After study of the Ni-TiO2@CaCO3 structure, it was then introduced into epoxy resin (EP) to improve the flame retardancy and thermal stability. The results shown that NiO and TiO2 were supported on the surface of the CaCO3, and 5 wt% CaCO3 could enhance the flame retardancy and Ni-TiO2@CaCO3 further increased the flame retardancy of the EP composites. In the cone calorimeter test (CCT), the values of the peak heat release rate (pHRR) and smoke production rate (pSPR) were reduced to 769 kW/m2 and 0.32 m2/s by CaCO3 from 1101 kW/m2 and 0.39 m2/s of the raw EP respectively. Moreover, pHRR and pSPR values were further decreased to 511 kW/m2 and 0.25 m2/s by Ni-TiO2@CaCO3 respectively. Although the degradation temperature values were lower than that of the control EP, the temperature values at 5 and 50% mass loss for Ni-TiO2@CaCO3/EP composites were improved compared to the EP. In addition, the char residues value of the Ni-TiO2@CaCO3/ EP composite (23.5%) was obviously improved compared to that of the EP (13.0%) and CaCO3/ EP composite (16.4%). In addition, the flame retardancy mechanism of the Ni-TiO2@CaCO3/ EP composite was thoroughly analyzed by TGA-FTIR, FITR and Raman methods. This work provides a promising evaluation strategy for utilizing CaCO3 and its derivatives for possible treatment of EP to enhance its flame retardancy and thermal stability.